Why Your Doctor Uses Medical Imaging
Imaging techniques, such as X-rays, MRIs and ultrasound scans, provide reliable and detailed pictures of the inside of the body. Today, most of these techniques use computer technology to create high-resolution images with little risk and discomfort to patients.
If you're scheduled for an X-ray or imaging test, here are some things you should know about various procedures, what they're used for and any risks involved.
X-rays are beams of ionizing (high-energy) radiation that pass through the body and onto an X-ray detector plate or digital technology. The image that results is called a radiograph. The dense tissues of the body, such as teeth and bones, block X-rays and appear white on the radiograph. The less dense tissues, such as muscles or blood, do not block as much of the X-rays and appear gray or black. X-ray radiographs are inexpensive, quick and easy to obtain. A doctor most often uses X-rays to look at bone breaks, fractures, dental cavities, and abnormalities in internal organs. Chest X-rays look for an enlarged heart or damaged lung tissue. Low-dose X-rays look at soft tissue and are used for mammograms and for measuring bone density. X-rays pose no immediate health risks. Lead aprons are sometimes placed over areas of the body, such as reproductive organs, which are sensitive to radiation.
Computed tomography (CT scanning) uses a series of X-ray beams to produce cross-sectional images through the body. The X-rays are sent to a computer that builds up cross-sectional images and displays them on a monitor. Doctors often use CT scans to look at the brain after a stroke or if a tumor is suspected. Abdominal scans can detect tumors and diagnose kidney disease. You may want to ask your health care provider about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time. If you are pregnant or think you may be pregnant, you should notify your health care provider.
Magnetic resonance imaging (MRI) is a computer-assisted technique using a magnetic field and radio waves to create highly detailed cross-sectional images. MRIs can detect tumors and other abnormalities in the brain and assess injuries and detect causes of pain in the spine. Because MRIs don't involve ionizing radiation, they present fewer risks than X-rays, which do use ionizing radiation. Some people are uncomfortable with the enclosed, noisy nature of MRIs. Open MRIs are now available at many facilities. They may have larger openings or be open on 3 sides and offer benefits for overweight patients and people prone to claustrophobia.
Ultrasound scanning uses high-frequency sound waves that travel through the body and are viewed on a video screen. It creates pictures of organs to detect abnormalities. Pregnant women often have ultrasounds to check the development of a fetus. Ultrasound scans have no known risks.
- Bass, Pat F. III, MD, MPH
- MMI board-certified, academically affiliated clinician